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By NRL Corporate Communications
Pulling the pieces together
Historically, meteorologists and oceanographers designed and employed discrete models of Earth systems to produce individual forecasts: ocean models to predict the ocean circulation; atmospheric models for the weather; sea ice models to predict the cryosphere; and wave models for the ocean surface.
Researchers knew the Earth’s environmental conditions were linked even though the models were seldom interdependent.
“We've realized for some time that these processes are all coupled,” said James Doyle, PhD, a senior scientist with Marine Meteorology Division. “The atmosphere is exchanging information with the ocean in terms of temperature and moisture, and even the currents can affect the winds in the low levels to some degree.”
Metzger said wind stress and heat exchanges at the ocean surface can impact ocean currents, waves, the sea ice cover as well as the entire ocean thermal structure.
“Things like El Niño, for example – they’re inherently coupled phenomena. They come about because of the way the ocean and the atmosphere talk to each other,” Reynolds said. “We're coupling all these systems together with the hope—and I think we have evidence that it's working — that we'll be able to capture some of these coupled phenomena that have predictability on longer time ranges.”
Four years? Why is it taking so long?
Each model has its own grid of the Earth, a massive set of data points. Imagine the latitude and longitude lines crisscrossing a globe. Each intersection of the lines marks a grid point where the model equations are solved over and over again from the top of the atmosphere to the bottom of the ocean.
Each model’s grid is different, and the grids inside individual models can also vary.
For example, the distance between grid points for HYCOM, the ocean model, is only about four kilometers near the Equator, but this narrows to less than two kilometers near the North Pole. Imagine a grid spanning the entire Earth with points less than four kilometers apart — that's an exceptionally large number of grid points and makes ESPC computationally expensive to run.
To enable the models to interact with each other, NRL scientists work with scientists from the National Oceanic and Atmospheric Administration, NASA, universities and research laboratories to develop the Earth System Modeling Framework. It’s essentially a coupler to allow the different model grids to exchange information.
And though the models themselves work well on their own, they don't necessarily work well when they start talking to each other. They have to cooperate. So much of their work in model development involves adjusting the models themselves.
“It’s a relatively easy engineering problem to wire the models together, but the real science comes in the research to make sure the physics of each model have the proper feedbacks when exchanging information,” said Metzger.
“It took us quite a bit of time to get our models improved -- at least for the atmospheric model,” Reynolds said. “We spent a lot of time modifying the model so that it would behave well in a coupled system.”
Four years into system development is atypical, Reynolds said. From conception to deployment, it can take on the order of 10 years or so to construct these systems. It’s taking less time to develop ESPC because they’re building the coupled system from preexisting component systems.
After the ESPC debuts, researchers will continue refining and improving the system. The system’s final operating capability is scheduled for fiscal year 2022.
About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the Navy and Marine Corps from the seafloor to space and in the information domain. NRL headquarters is located in Washington, D.C., with major field sites in Stennis Space Center, Mississippi, Key West, Florida, and Monterey, California, and employs approximately 2,500 civilian scientists, engineers and support personnel.